Process for the manufacture of 3-formylrifamycin-sv



United States Patent O 3,524,845 PROCESS FOR THE MANUFACTURE OF S-FORMYLRIFAMYClN-SV Hans Bickel, Binningen, and Wilhelm Kump, Therwil, Switzerland, assignors to Cilia Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed May 21, 1968, Ser. No. 730,911 Claims priority, application Switzerland, May 29, 1967, 7,533/ 67 Int. Cl. C07c 47/18 US. Cl. 260-410 12 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION As is known, 3-formylrifamycin has very good antibacterial properties and is also a very important intermediate for the manufacture of numerous derivatives of high antibiotic activity, especially of its functional aldehyde derivatives, for example of the hydrazones. 3-formylrifamycin-SV, which corresponds to the following partial structural formula OH OH r t H is accessible by the hitherto known process by oxidizing 3-aminomethylrifamycin-SV derivatives of the partial structural formula CHO OH 0 A? H o k ClilzNRR' I OH CH o where R and R' represent hydrogen, alkyl, aralkyl, cycloalkyl or, together with the nitrogen atom, the residue of a heterocyclic compound containing one or more than one hetero atom with a mild oxidizing agent in a suitable solvent. Suitable oxidants are more especially alkylnitrites, lead tetraacetate, persulfates, 1,4-quinones, oxygen in the presence of a catalyst, potassium ferricyanide or manganese dioxide (see British Pat. 1,109,631). The solvent used depends on the oxidant concerned, for example the oxidation with an alkylnitrite or with lead tetraacetate is preferably performed in a halogenated hydrocarbon such as chloroform or carbon tetrachloride, if desired or required, with addition of an aliphatic car- 3-formylrifamycin-SV.

lce

boxylic acid, such as acetic acid. The oxidation is carried out at room temperature and should take from 2 to 24 hours depending on the starting material used. Before isolating the oxidation product it is possible to carry out a treatment with ascorbic acid.

It appears that in this process, apart from the desired formation of 3-formylrifamycin-SV, also further reactions occur which give rise to undesired by-products so that the yields of 3-forrnylrifamycin-SV are always very moderate and never exceed of the theoretical.

SUMMARY OF THE INVENTION The present invention provides a new process for the manufacture of 3-formylrifamycin-SV in a high yield and by a smooth reaction from 3-aminomethylrifamycin-SV derivatives. It is characterized in that a 3-aminomethylrifamycin-S compound of the formula CH3 CH8 CH3 I 0113000 H OH 0 (I30 CH2 CH3 CH8 l NH CHaO I 2 0 H CH2-R Ha (V) where R represents a free or substituted amino groupis irradiated with ultraviolet light in an anhydrous or aqueous solvent at a low temperature and a possibly obtained 3-aldehyde derivative of 3-formylrifamycin-SV is hydrolysed.

The starting materials of the above Formula V in pure form and obtainable by a specific process and pharmaceutical preparations containing such compounds which have antibacterial activity, also pertain to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The new process of the present invention for the manufacture of formyl-rifamycin-SV from compounds of the Formula V may be illustrated by the following partial formulae scheme:

This new process is based on the finding that when 3- aminomethyl-rifamycin-S compounds (I) are irradiated with ultraviolet light in a suitable solvent, such as alcohol, they are converted into compounds (II) which are very easy to hydrolyze and thereby furnish readily 3- formylrifamycin-SV (III) or (IV) respectively. It may be assumed that during the irradiation a tautomerization takes place and the starting materials are transformed quantitatively into aldehyde derivatives 11 which are very easy to solvolize, especially to hydrolyze with water, and thereby furnish 3-formylrifamycin-SV derivatives or free B-fOrmylrifamycin-SV.

In the above Formula V, R represents a free amino group or an amino group substituted by one or two aliphatic, aromatic, cycloaliphatic, araliphatic or heterocyclic residues. Aliphatic hydrocarbon residues may also be interrupted in the carbon chain by hetero atoms such as oxygen, nitrogen or sulphur atoms, and/or they may be substituted by one, two or more identical or different functional groups such as hydroxyl groups, halogen atoms, free or esterified carboxyl or sulphonic acid groups, aldehyde groups, nitrile or amino groups. Preferably, they do not contain more than 12 carbon atoms and contain in the first place from 1 to 8 carbon atoms. Suitable residues are, above all, saturated or monounsaturated residues, for example lower alkyl, alkenyl, alkylene, cycloalkyl, cycloalkenyl, cycloalkylalkyl or cycloalkenylalkyl groups, or phenylalkyl such as phenyllower alkyl residues, in which the phenyl residues may be unsubstituted or contain one, two or more identical or different substituents such as lower alkyls, lower alkoxy groups, halogen atoms or carboxyl groups. As relevant examples there may be mentioned methyl, ethyl, hydroxy-ethyl, allyl, methallyl, propyl, isopropyl residues; straight or branched butyl, pentyl, hexyl or heptyl groups which may be linked in any desired position; butylene- (1,4), pentylene-(1,5), hexylene(l,6), hexylene-(l,5), hexylene-(2,5), heptylene-(2,7), heptylene-(2,6); cyclopentyl, cyclohexyl-, cyclopentenyl-, cyclohexenyl-methyl or -ethyl groups; benzyl, p-chlorobenzyl, p-methoxybenzyl, l-phenyl-ethyl or Z-phenyl-ethyl.

Preferred starting products are those of the above Formula V in which R represents a monoor di-lower alkyl-amino group or an alkylene-, oxa-, thiaor azaalkyleneamino group or a phenylor N-lower alkyl-N- phenylamino group, for example especially the methyl amino, ethylamino, propylamino, butylamino, anilino, toluidino, N-methylanilino group or a dimethylamino, diethylamino, dipropylamino, or diisopropylamino, pyrrolidino, piperidino, morpholino, l-methylpiperazino, 4- carboxypiperidino, 2,5-dihydroxymethylpyrrolidino, N- methylcyclohexylamino, 2-methylpiperidino or 4-methylpiperidino group.

The irradiation is performed at a low temperature, preferably below C., for example at to C., using natural or artificially produced ultraviolet light such as is emitted, for example, by mercury high-pressure or low-pressure burners, for example those of the type I-Ianau Q-8l. The reaction is complete in most cases after a short time, about 5 to 10 minutes. In general, the irradiation product is of a deep red coloration.

Suitable solvents are above all alcohols, especially lower aliphatic alcohols having a branched carbon chain, such as isopropanol, tertiary butanol or isoamyl alcohol, ethers, especially cyclic ethers such as dioxane, ketones or dimethylformamide or diethylformamide. These solvents may be used in the anhydrous form or they may contain water.

The solution obtained by irradiation in an anhydrous medium probably contains a compound of the type (II) defined above or a corresponding functionally modified hydroxymethylene compound formed by solvolysis, for example alcoholysis, which on addition of water is readily hydrolyzed to 3-formylrifamycin-SV. In the presence of water a hydrolysis leading to S-fQrmylrifamycin-SV may even have taken place already during the irradiation so that this compound, too, may be present in the irradiation solution.

For the manufacture of 3-formylrifamycin-SV the said compounds present in the irradiation solution or the mixture as a whole is subjected to hydrolysis, most advantageously with water, for example by adding a small quantity of water directly to the irradiation solution and allowing the whole to stand for some length of time, for example for 12 to 48 hours, at room temperature. After having evaporated the solvent pure 3-formylrifamycin- SV is accessible from the residue by the usual purifying methods, such as crystallization or chromatography. This process gives yields of about of the theoretical of 3- formylrifamycin-SV referred to the weight of B-aminomethyl-rifamycin-S used initially.

The 3-aminomethyl-rifamycin-S compounds of the above Formula V to be used as starting materials can be prepared from the corresponding hydroquinones, some of which are known [cf. for example British Pat. 1,090,115 or Journ. Med. Chem. 8 page 790(1965)] in known manner by mild oxidation, for example with air or oxygen, persulphates, potassium ferricyanide or alkylnitrites. New 3-aminomethyl-rifamycin-SV compounds are accessible in known manner, for example by reacting rifamycin-S with at least 2 molecular equivalents of formaldehyde and an excess of the amine corresponding to the amino group to be introduced.

According to a particularly advantageous manner of manufacturing the starting materials of the above Formula V the corresponding 3-aminomethyl-refamycin- SV compounds are treated in a suitable organic solvent at a temperature of at most about 0 C. with excess potassium ferricyanide solution, if desired extracted at the same temperature with a water-immiscible solvent, the organic phase is separated, dried and freed from the solvent at a low temperature. In this manner it is possible to obtain quantitative yields of pure quinones which in the past had been isolated exclusively in the form of mangano salts.

The treatment with potassium ferricyanide solution may be carried out in a homogeneous or heterogeneous phase. It is advantageous to dissolve the starting materials in water-immiscible organic solvents, especially hydrocarbons, for example chlorinated aliphatic hydrocarbons such as chloroform, methylenechloride or carbon tetrachloride. On completion of the oxidation the organic phase is separated at a temperature below 0 C., then dried and finally freed from solvent at a low temperature. When the oxidation is carried out in a water-miscible solvent such as dioxane or a ketone such as acetone, or in dimethylformamide, the reaction mixture is always extracted at a temperature below the freezing point with a water-immiscible organic solvent, for example one of those mentioned above and then further worked up as described.

Another object of the present invention are, therefore, compounds of the above Formula V in pure form and the special process for their manufacture described above.

The compounds of the above Formula V are also important as antibiotically active compounds having a high antibacterial activity against Gram-positive and Gramnegative bacteria and being little toxic. Thus, for instance, both in vitro and in vivo, they develop, for example on infected mice, a strong antibacterial activity against Staphylococcus aureus and Mycobacterium tuberculosis. They may thus be used as medicaments in the treatment of bacterial infections.

Of special value are the above-mentioned groups and specific compounds of this type of compounds.

The present invention includes also any variant of the present process in which an intermediate obtained at any stage is used as starting material and any remaining steps are carried out or in which a starting material is formed under the reaction conditions.

The present invention includes also the manufacture of pharmaceutical preparations for use in human and veterinary medicine which contain the pharmacologically active S-aminomethyl-rifamycin-S compounds of the Formula V, accessible in pure form by the process described above, especially the compounds in this class mentioned as particularly active, as active ingredients together with a pharmaceutical excipient. The excipients used are organic or inorganic substances suitable for enteral, for example oral, parenteral or local administration. Suitable excipients are substances that do not react with the new compounds, for example water, gelatin, lactose, starches, marnesium stearate, talcum, vegetable oils, benzyl alcohols, gums, polyalkyleneglycols, white petroleum jelly, cholesterol or other known medicinal excipients. The pharmaceutical preparations may be solid, for example tablets, dragees or capsules, or liquid or semi-liquid, such as solutions, suspensions, emulsions, ointments or creams. These pharmaceutical preparations may be sterilized and/ or contain assistants such as preserving, stabilizing wetting or emulsifying agents, salts for regulating the osmotic pressure or buflfers. They may also contain other therapeutically valuable substances. The new compounds may also be used as starting materials for the manufacture of other valuable compounds.

The above compounds of the Formula V may also serve as additives to animal fodder.

The following examples illustrate the invention. The thin-layer of chromatograms mentioned therein have been obtained on silicagel impregnated with citric acid in the system chloroform+acetone 3:1. The Rf values are referred to the Rf value of 3-diethylamiuomethyl-rifamycin-SV=1, and are here designated as R Example 1 A solution of 3-diethylaminomethyl-rifamycin-SV (Rf =1) in chloroform is cooled to C. and mixed at 0 C. with excess aqueous potassium ferricyanide solution alkalinized with sodium bicarbonate. While carefully cooling the mixture to 0 C., it is vigorously agitated for minutes. The chloroform phase is then separated, cooled to C., dried with sodium sulphate and evaporated at this temperature. The residue consists of pure, amorphous 3-diethylaminomethyl-rifamycin-S (Rf =0.0) and is soluble in chloroform, dimethylformamide and in alcohols. The yield is quantitive. The substance can be reconverted quantitatively into 3-diethylaminomethyl-rifamycin-SV by means of ascorbic acid.

50 mg. of the resulting 3-diethylaminomethyl-rifamycin- S are dissolved at 10 C. in 2 ml. of dimethylformamide and diluted with /z-litre of isopropanol cooled to '10 C. The solution is introduced into a /z-litre sulphating flask provided with magnetic stirrer and cooling bath and cooled to -20 C. The batch is then irradiated for 5 minutes with an immersion lamp (mercury high-pressure burner Hanan Q-81), while stirring and cooling well to maintain the temperature between C. and C. After the irradiation the reaction solution contains mainly a red-coloured substance (Rf =1.67) which, when allowed to stand in aqueous isopropanol, is converted into 3-formyl-rifamycin-SV. The cooling bath is removed, 5 ml. of water are added to the irradiated solution and the whole is kept for 3 days at room temperature. Finally, it is evaporated and the resulting 3-formylrifamycin-SV is purified by chromatography (on silicagel, with chloroform+10% acetone), to yield 42 mg. of 3-formylrifamycin-SV (Rf =8.6) which crystallize from tetrahydrofuran. Yield: 90% of the theoretical.

Example 2 3 g. of potassium ferricyanide and 500 ml. of water are added to a solution of 2.0 g. of 3-piperidinomethylrifamycinSV in 200 ml. of methanol, a clear, dark-red solution being obtained. The reaction mixture is allowed 6 to stand for 5 minutes at 20 C., is acidified with citric acid and extracted with chloroform. After drying and evaporating the chloroform in vacuo, there are obtained 2 g. of 3-piperidinomethyl-rifamycin-S of Rf =0.

50 mg. of 3piperidinomethyl-rifamycin-S are dissolved in 500 ml. of isopropanol. The solution is irradiated in a 500 ml. sulphonating flask at 20 C. for seven minutes with an immersion lamp Hanau Q-81. After irradiation, the reaction solution contains mainly a red-coloured substance (Rf =l.80). 5 ml. of water are added to the irradiated solution and the batch is allowed to stand at room temperature for 3 days. Finally, it is evaporated and the 3-formyl-rifamycin-SV formed is purified by chromatography (on silicagel, chloroform with 10% acetone). More than 42 mg. of 3-formylrifamycin-SV (Rf =8.6) are obtained. The product can be recrystallized from tetrafuran.

We claim:

1. A B-aminomethyl-rifamycin-S compound of the formula in which R represents a member selected from the group consisting of amino, amino substituted by a member selected from the group consisting of lower alkyl, lower alkenyl, lower alkyl substituted by a member selected from the group consisting of hydroxy, halogen, carboxy, cyano and amino, lower alkenyl substituted by a member selected from the group consisting of hydroxy, halogen, carboxy, cyano and amino, lower alkylene; cyclo-lower alkyl, cyclo-lower alkenyl, cyclo-lower alkyl-lower alkyl, cyclolower alkenyl-lower alkyl, monocyclic aryl, monocyclic aryl-lower alkyl, monocyclic aryl substituted on the aryl portion by a member selected from the group consisting of lower alkyl, lower alkoxy, halogen and carboxyl, monocyclic aryl-lower alkyl substituted in the aryl portion by a member selected from the group consisting of lower alkyl, lower alkoxy, halogen and carboxyl; lower alkyleneamino; oxa-lower alkyleneamino; thia-lower alkyleneamino, and aza-lower alkyleneamino, in pure form.

2. A compound as claimed in claim 1, wherein in the formula R is an amino group substituted by a member se lected from the group consisting of one and two aliphatic, aromatic, cycloaliphatic, araliphatic and heterocyclic hydrocarbon radicals having from 1 to 8 carbon atoms, in pure form.

3. A compound as claimed in claim 1, wherein in the formula R is a mono-lower alkylamino group, in pure form.

4. A compound as claimed in claim 1, wherein in the formula R is a di-lower alkylamino group in pure form.

5. A compound as claimed in claim 1, wherein in the formula R is a member selected from the group consisting of pyrrolidino, piperidino, piperazino and morpholino, in pure form.

6. A compound as claimed in claim 1, which is the 3- diethylamino-rifamycin-S, in pure form.

7. A compound as claimed in claim 1, which is the 3- piperidinomethyl-rifamycin-S, in pure form.

8. A process for the preparation of a compound of formula in which R represents a member selected from the group consisting of amino, amino substituted by a member selected from the group consisting of lower alkyl, lower alkenyl, lower alkyl substituted by a member selected from the group consisting of hydroxy, halogen, carboxy, cyano and amino, lower alkenyl substituted by a member selected from the group consisting of hydroxy, halogen, carboxy, cyano and amino, lower alkylene; cycle-lower alkyl, cyclo-lower alkenyl, cyclo-1ower alkyl-lower alkyl, cyclo-lower alkenyl-lower alkyl, monocyclic aryl, monocyclic aryl-lower alkyl, monocyclic aryl substituted on the aryl portion by a member selected from the group consisting of lower alkyl, lower alkoxy, halogen and carboxyl, monocyclic aryl-lower alkyl substituted in the aryl portion by a member selected from the group consisting of lower alkyl, lower alkoxy, halogen and carboxyl; lower alkyleneamino; oxa-lower alkyleneamino; thia-lower alkyleneamino and aza-lower alkyleneamino, wherein the corresponding 3-aminomethyl-rifamycin-SV compound is treated in a suitable organic solvent at a temperature of at most about 0 C. with excess potassium ferricyanide solution, the oxidized compound is extracted from the reaction mixture with a water-immiscible organic solvent, the organic phase is separated, dried and freed from the solvent at a low temperature.

9. A process as claimed in claim 8, wherein an aqueous potassium ferricyanide solution is added to a solution of the starting material in a water-immiscible solvent.

10. A process as claimed in claim 8, wherein an aqueous potassium ferricyanide solution is added to a solution of the starting material in a member selected from the group consisting of methylene chloride and carbon tetrachloride.

11. A process as claimed in claim 8, wherein an aqueous potassium ferricyanide solution is added to a solution of the starting material in a member selected from the group consisting of dioxan, acetone, dimethylforrnamide and the oxidation mixture is extracted with a member selected from the group consisting of methylene chloride and carbon tetrachloride.

12. A process as claimed in claim 8, wherein an aqueous potassium ferricyanide solution is added to a solution of the starting material in a lower aliphatic alkanol and the oxidation mixture is extracted with a member selected from the group consisting of methylene chloride and carbon tetrachloride.

References Cited FOREIGN PATENTS 1,090,115 1967 Great Britain.

OTHER REFERENCES Maggi et al.: Jour. Med. Chem, vol. 8, 1965, pp. 790-793.

LEWIS GO'ITS, Primary Examiner I. R. BROWN, Assistant Examiner US. Cl. X.R. 

